Definitely respiratory got him in the end alright...his gills were going 90 miles a minute this morning....and the way you describe it is exactly the way it happened. It looked like he was trying to take one final gasp for air.... terrible to see.
So I guess he was laboring over this for some days, but I just didn't spot it.
I think their number was up from day one. Its just frustrating for me.
Anyway. Just for the record...here's what I read up on columnaris:
Symptoms:
White spots on mouth, edges of scales, and fins
Cottony growth that eats away at the mouth
Fins disintegrate beginning at the edges
'Saddleback' lesion near the dorsal fin
Fungus often invades the affected skin
Rapid gilling in cases where gills are infected
The gills filaments will disintegrate as the bacteria invade them, and the fish will begin breathing rapidly due to lack of oxygen. Less commonly, the infection will be internal, and display no external symptoms.
So now....sounds alot like it.